1. Field of the Invention
The present invention relates to a data communication system which is particularly useful for applications which suffer from noisy channels.
2. Description of the Related Art
In data communication systems, automatic repeat request is a well known mechanism for recovering transmission errors. A timer is started when the transmit end sends an information frame and waits for acknowledgment. When an acknowledgment frame is not returned from the receive end within a predefined time interval set by the timer, the transmit end recognizes that the transmitted frame is corrupted and retransmits a copy of the transmitted frame. The time interval of the timer is usually determined based on the time taken for the receive end to acknowledge a transmitted frame. If transmitted frames are lost or corrupted due to channel noise, timeouts and retransmissions are repeated at the transmit end, severely deteriorating the throughput of the network. In addition, transmission delays unexpectedly occur in communications networks. Due to transmission delays, timeouts occur even if transmitted frames are received at the distant end. If a communication channel contains a noisy section such as wireless link, transmission delays of the network would cause the transmit end to repeat unnecessary retransmissions over the wireless link, and the throughput of the network is severely degraded.
It is therefore an object of the present invention to provide a high throughput wireless data communication method and system.
The object of the present invention is obtained by reducing overhead of packets of a data communication network by transferring communication protocol data from a wireless section to a land-line section of the network.
According to a first aspect of the present invention, there is provided a data communication method comprising establishing a first connection over a wireless link between a first site and a second site and a second connection between the second site and a third site over a land-line network, transferring, from the first site to the second site, communication protocol data necessary for communication control with the third site, receiving, at the second site, a data signal from the first site and converting the received data signal into a packet according to communication protocol defined by the transferred protocol data between the second site and the third site and transmitting the packet to the third site, and receiving, at the second site, a data signal from the third site and converting the received data signal into a packet according to communication protocol defined by the transferred protocol data between the second site and the first site and transmitting the packet to the first site.
According to a second aspect, the present invention provides a data communication method comprising establishing a connection between first and second sites, dividing data, at the first site, into a plurality of data blocks of first length according to a record of packets in error received at the first site, and transmitting the data blocks in packets of the first length from the first site over the established connection to the second site, receiving the transmitted packets at the second site, evaluating the received packets and returning a signal from the second site to the first site, requesting data blocks to be retransmitted, if there is at least one packet in error or lost, and receiving the signal at the first site, dividing the data blocks requested by the received signal into blocks of second length smaller than the first length and transmitting the divided data blocks in packets of the second length over the established connection from the first site to the second site.